In order to retain the rollers or other rotary bodies in the clearance between the two bearing races, the ends of that clearance may be obstructed by annular disks secured to either or both of the coaxial members. For safe operation it is desirable that these obstructions should cover well over half the radial width of the clearance, yet a single disk rigid with either the inner or the outer member would generate considerable frictional heat by its contact with the adjoining rotary bodies, particularly in the case of a high-speed roller bearing. The art therefore prefers to use two pairs of disks each projecting by less than half the clearance width beyond the corresponding peripheral surface. If both pairs of disks are bolted or otherwise fixedly secured to their respective bearing member, a disassembly for replacement of parts, regrinding of surfaces or any other purpose would be difficult. The practice, therefore, has been to make one pair of disks--usually the outer pair--detachable from the associated member.
In commonly owned German published specification No. 2,503,916 there is disclosed a boundary disk of this type in the form of a flat ring held in position on an end face of an outer bearing member by a bayonet coupling consisting of peripherally spaced-apart retaining lugs on the bearing member and similarly spaced coacting lugs on the disk. In order to retain that disk in the locking position of the bayonet coupling, the end face and the confronting lug surfaces may be made slightly convergent to produce a wedging effect. From commonly owned German published specification No. 2,830,818 it is further known to provide a boundary disk in the form of a split flat ring which fits into a pheripheral groove on an end face of an outer bearing member and is retained in that groove by a spreader inserted between the ring segments separated by the split.